1. Field of the Invention
This invention relates generally to tobacco and reconstituted tobacco smoking materials and methods of making same. More particularly, the present invention relates to the materials and methods that provide tobacco materials with reduced nitrogenous content and also provide reconstituted tobacco paper with leaf-like characteristics.
2. Description of the Related Art
Tobacco material contains various nitrogenous compounds that can adversely affect its smoke quality. Among these nitrogenous compounds are proteins, amino acids and certain alkaloids, such as nicotine, nornicotine, anabasine and anatabine. The smoke quality of tobacco is adversely affected particularly by heterocyclic and aromatic amines, and tobacco specific nitrosamines (TSNA), as well as other compounds formed by pyrolysis or transfer of these nitrogenous compounds. Tobacco processing sometimes includes steps in which the nitrogen content of the tobacco is reduced, so as to improve the smokability of the tobacco. However, nitrogenous compounds, especially proteins, are difficult to extract from cured tobacco lamina, stem, and fiber cell walls.
Insoluble proteins make up more than 90% of the total proteins found in cured tobacco. These insoluble proteins are globular in conformation, and are bound to lipoidal organocellular membranes of fiber or cellulose cell walls. Solubilization and extraction of these insoluble proteins have traditionally proven difficult when using water or solvents under moderate digestion conditions (i.e. less than 100xc2x0 C. and 65-70 psig) and with shredded tobacco of size suitable for cigarette manufacture. This difficulty is due in large part to the compact and rigid structure of fiber cells. Penetration of rigid cell wall structure by solvents has proven feasible only after thermal and/or mechanical sample treatment. However, the common result of such sample treatment is poor recovery of the solvated particulate material. Moreover, cell wall penetration does not necessarily lead to protein solubilization, since plant proteins differ in their conformity and solubilization patterns. More specifically, plant proteins are divided into four major classes: albumins; globulins; prolamins (also known as gliadins); and, glutelins. Albumins are soluble in water, whereas globulins are soluble in dilute salt solutions. Prolamins are soluble in dilute acid or alkali solutions, while glutelins are soluble in alcohol solutions. Some proteins, however, overlap into two of these four classifications, thereby increasing the difficulty of accurately predicting the appropriate diluent.
Many of the current processes used to reduce nitrogen content in tobacco material employ enzymatic compounds and microbial agents to break down the proteins and other nitrogen-containing compounds within the tobacco. However, disadvantages arise from the use of such enzymatic compounds and agents. In particular, enzymes are expensive, pH sensitive and degrade proteins into amino acids which tend to remain with the tobacco material. It is also thought that enzymatic compounds leave residues on tobacco material after processing. Furthermore, microbial agents used in treating tobacco tend to cause unwanted reactions that generate undesirable by-products.
Therefore, there is a need to provide a process by which the nitrogen content of tobacco material may be reduced without leaving residues or undesirable by-products. This process must provide effective solubilization of proteins and other nitrogenous compounds, as well as adequate particulate matter recovery.
The present invention relates to a method for providing a reconstituted tobacco material having a reduced nitrogenous content. The tobacco material in the form of flue cured and burley whole leaf, stems, fines, lamina or scraps, and/or burley stems are contacted with an aqueous solvent. The resulting liquid extract is separated from the tobacco fiber portion. The tobacco fiber portion is then contacted with a solution containing sodium acetate and/or sodium hydroxide and/or potassium hydroxide. This solution is also separated from the tobacco fiber portion. The tobacco fiber portion may then be washed, refined and processed into reconstituted tobacco sheets. The liquid extract from the aqueous solvent extraction may be concentrated and added back to the sheets. These sheets may then be used in smoking articles, such as cigarettes. The reduction of nitrogenous compounds in the tobacco material provides for improved smokability and a reduction in nitrogen containing pyrolitic products emitted from smoking articles which contain the tobacco material.
It is an object of the present invention to provide a reconstituted tobacco material with reduced levels of nitrogenous compounds.
It is another object of the present invention to provide a method of making a reconstituted tobacco material with reduced levels of nitrogenous compounds.
It is a further object of the present invention to provide a reconstituted tobacco material paper with a cured tobacco leaf-like texture.
More particularly, the present invention is directed to a method for reducing the nitrogenous content of tobacco material, including cured tobacco whole leaf, fines, scraps, stems, and lamina, as well as burley leaf and stem, comprising the steps of: contacting tobacco material with a first aqueous solvent, such as water, at a temperature of about 60xc2x0 C. to 80xc2x0 C. for about 0.5 to 1 hour; separating the aqueous tobacco extract from the tobacco fiber portion; contacting this washed tobacco fiber portion with a solution containing 0.10% to 10% (weight/volume) sodium acetate and/or 0.1% to 10.0% (weight/volume) sodium hydroxide and/or 0.1% to 10.0% (w/v) potassium hydroxide at a pH of about 3.5 to 14 and a temperature of about 50xc2x0 C. to 150xc2x0 C. for about 0.25 to 24 hours; and, then separating the solution from the tobacco fiber portion. Preferably, the solution will contain about 0.75% to 1.0% (w/v) sodium acetate and/or 0.5% to 1.0% (w/v) sodium hydroxide and/or 0.5% to 1.0% (w/v) potassium hydroxide.
Furthermore, the present invention is directed to a reconstituted tobacco sheet formed from the tobacco material treated according to the above method. The reconstituted tobacco sheet, formed from tobacco material treated according to the method in which the solution contains sodium hydroxide or potassium hydroxide in the absence of sodium acetate, exhibits physical characteristics superior to those exhibited by reconstituted tobacco sheets formed by conventional or other methods. More particularly, a reconstituted tobacco sheet formed from tobacco material treated thus has a texture and density similar to that of cured tobacco leaf. This tobacco sheet, when cut, is less likely to crumble than a reconstituted tobacco sheet formed by conventional methods, and it is stronger than either cured tobacco leaf or conventional reconstituted tobacco sheet.
A better understanding of the present invention will be realized from the hereafter processes and the Examples following such description